Tom Smykowski is a senior product engineer with nearly two decades of experience, specializing in architecting and implementing scalable, user-centric subscription billing systems for SaaS products. Hire him to solve complex billing logic, ensure compliance, and optimize the payment-to-revenue journey, whether you're launching an MVP or modernizing a legacy platform. He combines deep technical expertise in full-stack development with product and UX thinking, taking ownership from discovery through to production and ongoing iteration for teams across the EU, UK, and US.
The Critical Role of Billing Engineering in SaaS
In a subscription-based business, the billing system is the revenue engine. It's far more than a payment processor, it's a complex product layer that directly impacts customer trust, cash flow, and operational scalability. A well-architected billing system handles not just charging a card, but managing intricate subscription lifecycles, prorations, upgrades, downgrades, dunning processes, tax calculations, and compliance with regional regulations like VAT, SCA, and GAAP revenue recognition. Getting this right from the start, or successfully modernizing an existing system, requires an engineer who thinks beyond code to consider business logic, user experience, and financial integrity.
Many SaaS companies initially bolt on a third-party service like Stripe or Paddle, which is a sensible starting point. However, as the business grows, product offerings become more complex, and international expansion begins, the limitations of an off-the-shelf integration become apparent. You need custom logic for enterprise deals, nuanced trial structures, usage-based billing components, or complex partner revenue sharing. This is where a specialized subscription billing engineer becomes invaluable. They can design a system that leverages these powerful APIs while building the bespoke business logic and data models on top, creating a flexible, maintainable, and scalable revenue infrastructure.
Tom's experience spans the full spectrum, from founding his own fintech SaaS, Websoul, which served over 32,000 businesses, to scaling platforms like Printify for millions of merchants. This background means he understands the pressure points of billing systems at different stages of growth. He approaches billing not as a back-office function but as a core product feature that must be reliable, transparent, and easy for both end-users and internal finance teams to understand and manage.
Architecting Scalable and Compliant Billing Systems
The foundation of any robust SaaS billing platform is a scalable and well-documented architecture. This involves designing clear data models for plans, subscriptions, invoices, and payment methods, and establishing idempotent APIs that prevent duplicate charges or missed payments. A critical decision is determining the right balance between leveraging external payment service providers (PSPs) and maintaining control over your billing logic and customer data. An experienced engineer can architect a system where PSPs like Stripe, Braintree, or Adyen handle the secure payment flow and compliance, while your application controls the subscription rules, pricing models, and invoice generation.
Compliance is a non-negotiable layer in this architecture. For businesses selling in the EU, VAT MOSS rules require precise location-based tax calculation and reporting. Strong Customer Authentication (SCA) mandates secure payment flows. In the US, sales tax nexus rules add complexity. A billing engineer must bake these requirements into the system's design, not treat them as an afterthought. Tom's work with Croissant, a workplace platform, involved building compliant features, giving him direct experience in weaving regulatory requirements into product development. This proactive approach prevents costly re-engineering and potential legal issues down the line.
Furthermore, scalability isn't just about handling more transactions, it's about enabling business agility. Can marketing launch a new promotional pricing plan in hours, not weeks? Can the finance team run accurate revenue reports without engineering support? Can the system support a shift from flat-rate to hybrid usage-based pricing? Tom's product-minded engineering focuses on creating systems that empower other teams. By building clear admin interfaces, comprehensive logging, and well-designed APIs, he ensures the billing platform is a business enabler, not a bottleneck.
Implementing Complex Subscription Logic and Pricing Models
Modern SaaS rarely offers just a simple monthly or annual plan. The competitive landscape demands flexible pricing models that can be a key differentiator. Implementing these models requires precise engineering. Common scenarios include tiered pricing (e.g., Basic, Pro, Enterprise), per-seat licensing, usage-based or metered billing (e.g., API calls, gigabytes stored), one-time add-ons, and complex enterprise agreements with custom contracts and invoicing. Each model introduces edge cases: how do you prorate a mid-cycle upgrade when a user adds more seats and switches to a higher tier simultaneously? How do you track and bill for usage spikes accurately?
Tom's hands-on experience with TypeScript, Vue.js, and full-stack development is crucial here. He builds the frontend interfaces that allow customers to understand and select their plan, see upcoming charges, and manage their subscriptions with clarity. On the backend, he architects the services that calculate charges, generate invoices, and sync data with accounting systems. His work with AG Grid at Websoul, for instance, demonstrates an ability to handle complex, data-rich interfaces which are common in billing admin panels where teams need to view customer histories, payment failures, and revenue analytics.
Handling failed payments and dunning (the process of communicating with customers about failed payments) is another critical component of subscription logic. An automated, multi-step dunning process that includes email notifications, retry schedules, and graceful downgrades or suspensions can significantly reduce involuntary churn. Engineering this requires a reliable job queue system, templated communication, and a state machine to manage the subscription's status through the recovery process. Tom's systematic approach to product delivery ensures these crucial, revenue-protecting flows are built with the same care as the primary checkout experience.
Integrating Billing with the Broader Product and Tech Stack
A billing system does not operate in a vacuum. It is deeply integrated with nearly every other part of your application. When a user subscribes, the system must grant access to paid features. This requires tight integration with your authentication and authorization layer. Usage-based billing needs to pull metrics from your application's telemetry or logging systems. Revenue data must flow into your CRM (like Salesforce or HubSpot) for sales tracking and into your data warehouse (like BigQuery or Snowflake) for financial analysis and forecasting.
Tom's experience as a staff engineer at Croissant and his contributions to large-scale design systems at Printify, which served a platform of over 10 million merchants, have honed his skills in building cohesive, integrated systems. He understands how to design APIs and event-driven architectures (using tools like message queues or webhooks) that allow the billing module to communicate seamlessly with other services. This prevents the creation of siloed data and ensures a single source of truth for customer entitlements and financial data.
Furthermore, the billing experience is a key part of the overall user journey and brand perception. The checkout flow, invoice design, and account management portal should feel like a native part of your product, not a jarring third-party page. Tom's strong focus on UX and design systems ensures that the billing interfaces he builds are intuitive, accessible, and on-brand. He can lead the frontend implementation using modern frameworks like React or Angular to create a seamless experience that reinforces customer trust and reduces support tickets.
Modernizing Legacy Billing Platforms for Growth
Many established SaaS companies find themselves constrained by a billing system that was built for an earlier version of their business. Perhaps it's a monolithic codebase that is difficult to change, relies on deprecated APIs, or cannot support new pricing models required to enter a new market. The process of modernizing this critical system is high-stakes, as any error can directly impact revenue. It requires a careful, phased approach that minimizes risk while delivering incremental value.
Tom is well-versed in this challenge. His career includes modernizing systems for industrial and enterprise clients, such as his earlier work on industrial ERP systems at Insoft Serwis and his lead frontend role at Fream for industrial SaaS. This experience translates directly to billing modernization projects. A successful strategy often involves building a new, parallel billing service with a clean API, then gradually migrating customer cohorts or specific product lines over from the old system. This requires building robust data migration scripts, implementing feature flags, and ensuring both systems can coexist during the transition.
The goal of modernization is not just a tech stack upgrade, it's to unlock business capabilities. A modernized system should reduce the cost and time of launching new plans, improve the accuracy of financial reporting, decrease payment failure rates, and provide a better experience for both customers and internal teams. Tom's methodical ownership from architecture to production ensures the project stays aligned with these business outcomes. He doesn't just deliver code, he delivers a new, scalable revenue operations platform.
When This Is a Good Fit
Hiring Tom as your subscription billing SaaS engineer is an ideal fit if you are a founder, CTO, or product leader who needs to build a new billing system from the ground up, scale an existing one that's showing cracks, or modernize a legacy platform that's holding back growth. It's a perfect match if you value an engineer who takes full ownership, thinks deeply about product and UX, and can collaborate effectively with your finance, sales, and product teams. His remote work style from Poland, with availability for EU, UK, and US East Coast time zones, integrates seamlessly with distributed teams. If your priority is constructing a reliable, compliant, and scalable revenue engine that supports your business ambitions, let's connect.